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The spatial and temporal correlations between concurrent satellite observations of aerosol optical thickness (AOT) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and tropospheric columns of nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO) from the Ozone Monitoring Instrument (OMI) are used to infer information on the global composition of aerosol particles. When averaging the satellite data over large regions and longer time periods, we find significant correlation between MODIS AOT and OMI trace gas columns for various regions in the world. This shows that these enhanced aerosol and trace gas concentrations originate from common sources, such as fossil fuel combustion, biomass burning, and organic compounds released from the biosphere. This leads us to propose that satellite-inferred AOT to NO2 ratios for regions with comparable photochemical regimes can be used as indicators for the relative regional pollution control of combustion processes. Indeed, satellites observe low AOT to NO2 ratios over the eastern United States and western Europe, and high AOT to NO2 ratios over comparably industrialized regions in eastern Europe and China. Emission databases and OMI SO2 observations over these regions suggest a much stronger sulfur contribution to aerosol formation than over the well-regulated areas of the eastern United States and western Europe. Furthermore, satellite observations show AOT to NO2 ratios are a factor 100 higher over biomass burning regions than over industrialized areas, reflecting the unregulated burning practices with strong primary particle emissions in the tropics compared to the heavily controlled combustion processes in the industrialized Northern Hemisphere. Simulations with a global chemistry transport model (GEOS-Chem) capture most of these variations, although on regional scales significant differences are found. Wintertime aerosol concentrations show strongest correlations with NO2 throughout most of the

We present results from the OP3 campaign in Sabah during 2008 that allowus to study the impact of local emission changes over Borneo on atmospheric composition at the regional and wider scale. OP3 constituent data provide an important constraint on model performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty. Model studies of land-use change confirm earlier work, indicating that further changes to intensive oil palm agriculture in South East Asia, and the tropics in general, could have important impacts on air quality, with the biggest factor being the concomitant changes in NOx emissions. With the model scenarios used here, local increases in ozone of around 50 per cent could occur. We also report measurements of short-lived brominated compounds around Sabah suggesting that oceanic (and, especially, coastal) emission sources dominate locally. The concentration of bromine in short-lived halocarbons measured at the surface during OP3 amounted to about 7 ppt, setting an upper limit on the amount of these species that can reach the lower stratosphere.

The spatial and temporal correlations between concurrent satellite observations of aerosol optical thickness (AOT) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and tropospheric columns of nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO) from the Ozone Monitoring Instrument (OMI) are used to infer information on the global composition of aerosol particles. When averaging the satellite data over large regions and longer time periods, we find significant correlation between MODIS AOT and OMI trace gas columns for various regions in the world. This shows that these enhanced aerosol and trace gas concentrations originate from common sources, such as fossil fuel combustion, biomass burning, and organic compounds released from the biosphere. This leads us to propose that satellite-inferred AOT to NO2 ratios for regions with comparable photochemical regimes can be used as indicators for the relative regional pollution control of combustion processes. Indeed, satellites observe low AOT to NO2 ratios over the eastern United States and western Europe, and high AOT to NO2 ratios over comparably industrialized regions in eastern Europe and China. Emission databases and OMI SO2 observations over these regions suggest a much stronger sulfur contribution to aerosol formation than over the well-regulated areas of the eastern United States and western Europe. Furthermore, satellite observations show AOT to NO2 ratios are a factor 100 higher over biomass burning regions than over industrialized areas, reflecting the unregulated burning practices with strong primary particle emissions in the tropics compared to the heavily controlled combustion processes in the industrialized Northern Hemisphere. Simulations with a global chemistry transport model (GEOS-Chem) capture most of these variations, although on regional scales significant differences are found. Wintertime aerosol concentrations show strongest correlations with NO2 throughout most of the

Emission of bromine from sea-salt aerosol, frost flowers, ice leads, and snow results in the nearly complete removal of surface ozone during Arctic spring. Regions of enhanced total column BrO observed by satellites have traditionally been associated with these emissions. However, airborne measurements of BrO and O3 within the convective boundary layer (CBL) during the ARCTAS and ARCPAC field campaigns at times bear little relation to enhanced column BrO. We show that the locations of numerous satellite BrO "hotspots" during Arctic spring are consistent with observations of total column ozone and tropopause height, suggesting a stratospheric origin to these regions of elevated BrO. Tropospheric enhancements of BrO large enough to affect the column abundance are also observed, with important contributions originating from above the CBL. Closure of the budget for total column BrO, albeit with significant uncertainty, is achieved by summing observed tropospheric partial columns with calculated stratospheric partial columns provided that natural, short-lived biogenic bromocarbons supply between 5 and 10 ppt of bromine to the Arctic lowermost stratosphere. Proper understanding of bromine and its effects on atmospheric composition requires accurate treatment of geographic variations in column BrO originating from both the stratosphere and troposphere. Copyright 2010 by the American Geophysical Union.

Emission of bromine from sea-salt aerosol, frost flowers, ice leads, and snow results in the nearly complete removal of surface ozone during Arctic spring. Regions of enhanced total column BrO observed by satellites have traditionally been associated with these emissions. However, airborne measurements of BrO and O3 within the convective boundary layer (CBL) during the ARCTAS and ARCPAC field campaigns at times bear little relation to enhanced column BrO. We show that the locations of numerous satellite BrO "hotspots" during Arctic spring are consistent with observations of total column ozone and tropopause height, suggesting a stratospheric origin to these regions of elevated BrO. Tropospheric enhancements of BrO large enough to affect the column abundance are also observed, with important contributions originating from above the CBL. Closure of the budget for total column BrO, albeit with significant uncertainty, is achieved by summing observed tropospheric partial columns with calculated stratospheric partial columns provided that natural, short-lived biogenic bromocarbons supply between 5 and 10 ppt of bromine to the Arctic lowermost stratosphere. Proper understanding of bromine and its effects on atmospheric composition requires accurate treatment of geographic variations in column BrO originating from both the stratosphere and troposphere. Copyright 2010 by the American Geophysical Union.

Despite its low concentrations in the atmosphere, bromine monoxide (BrO) accounts for up to half of springtime catalytic ozone depletion in the stratosphere. In the troposphere, large quantities of BrO can appear suddenly and linger for several days. These bromine explosions have been linked to mercury deposition in the Arctic.Retrieval of BrO is difficult and measurements of bromine species at high latitudes are scarce. Therefore, there are large uncertainties in our knowledge of the amount of bromine in the atmosphere. In order to improve this situation, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. This research is an integral part the larger CANDAC (Canadian Network for the Detection of Atmospheric Change) project at PEARL to study Arctic atmospheric processes through 2007-2009, the International Polar Year (IPY), and beyond.We will discuss the techniques and challenges for ground-based BrO measurements. Furthermore, we will discuss comparisons between the ground-based measurements of BrO above Eureka and those made by the OSIRIS and OMI satellite instruments, distinguishing between tropospheric and stratospheric BrO concentrations.

Because measurements of bromine at high latitudes are scarce, the current understanding of bromine chemistry is largely based on model calculations. In order to help quantify the amount of bromine in the atmosphere, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. One of these instruments, the UT-GBS (University of Toronto Ground-Based Spectrometer), has been deployed at Eureka during polar sunrise since 1999. The other instrument, the PEARL-GBS (PEARL Ground-Based Spectrometer), was installed permanently in Eureka in August 2006 for year-round operation.The small signal and large diurnal variation of BrO are challenges for ground-based BrO retrievals. With zenith-sky measurements, we can retrieve vertical column densities of BrO, which are primarily sensitive to the stratosphere. We will discuss different methods for these retrievals and will compare our ground-based BrO vertical column density measurements with Ozone Monitoring Instrument on board the NASA Earth Observing System Aura satellite. Additionally, we are working on techniques to retrieve tropospheric partial columns of BrO using a combination of direct-sun measurements and zenith-sky measurements. We will discuss the status of these retrievals and future plans for tropospheric BrO measurements at Eureka.

Because measurements of bromine at high latitudes are scarce, the current understanding of bromine chemistry is largely based on model calculations. In order to help quantify the amount of bromine in the atmosphere, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. One of these instruments, the UT-GBS (University of Toronto Ground-Based Spectrometer), has been deployed at Eureka during polar sunrise since 1999. The other instrument, the PEARL-GBS (PEARL Ground-Based Spectrometer), was installed permanently in Eureka in August 2006 for year-round operation.The small signal and large diurnal variation of BrO are challenges for ground-based BrO retrievals. With zenith-sky measurements, we can retrieve vertical column densities of BrO, which are primarily sensitive to the stratosphere. We will discuss different methods for these retrievals and will compare our ground-based BrO vertical column density measurements with Ozone Monitoring Instrument on board the NASA Earth Observing System Aura satellite. Additionally, we are working on techniques to retrieve tropospheric partial columns of BrO using a combination of direct-sun measurements and zenith-sky measurements. We will discuss the status of these retrievals and future plans for tropospheric BrO measurements at Eureka.

Despite its low concentrations in the atmosphere, bromine monoxide (BrO) accounts for up to half of springtime catalytic ozone depletion in the stratosphere. In the troposphere, large quantities of BrO can appear suddenly and linger for several days. These bromine explosions have been linked to mercury deposition in the Arctic.Retrieval of BrO is difficult and measurements of bromine species at high latitudes are scarce. Therefore, there are large uncertainties in our knowledge of the amount of bromine in the atmosphere. In order to improve this situation, we measured BrO columns with two ground-based UV-visible spectrometers at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80oN, 86oW) in spring 2008. This research is an integral part the larger CANDAC (Canadian Network for the Detection of Atmospheric Change) project at PEARL to study Arctic atmospheric processes through 2007-2009, the International Polar Year (IPY), and beyond.We will discuss the techniques and challenges for ground-based BrO measurements. Furthermore, we will discuss comparisons between the ground-based measurements of BrO above Eureka and those made by the OSIRIS and OMI satellite instruments, distinguishing between tropospheric and stratospheric BrO concentrations.